With the identification of autoantigens in various autoimmune diseases, the use of self-peptide vaccines in the prevention and treatment of autoimmunity is becoming a possiblity. However, anaphylaxis has been observed with the use of self-peptides in experimental autoimmune encephalitis (EAE) and we have observed fatal anaphylaxis in type 1 diabetes in mice. Recently, a phase II trial of an altered peptide ligand in multiple sclerosis has also been complicated by hypersensitivity reactions. Finally, there is an altered peptide ligand trial for the insulin B:9-23 peptide (amino acids 9 through 23 on the insulin B chain) for type 1 diabetes currently underway in man. Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes. Treatment of NOD mice with subcutaneous B:9-23 peptide in saline protects from diabetes, but is associated with fatal anaphylaxis upon repeated administration. The purpose of this project is to evaluate a potential general mechanism to prevent peptide-induced anaphylaxis while preserving immunomodulation as it relates primarily to a vaccine for type 1 diabetes utilizing B:9-23. It is hypothesized that rapid systemic absorption of subcutaneous B:9-23 can be delayed by neutralizing the pl, avoiding anaphylaxis while retaining its immunologic properties. Preliminary data includes altering the pl of B:9-23 through the addition of 2 arginines (RR) at the C-terminus, changing the pl from 5.3 to near neutral. The specific aims are to i) confirm the ability of B:9-23RR to prevent anaphylaxis when injected subcutaneously but not intravenously ii) directly quantitate the systemic absorption of B:9-23 and B:9-23RR and correlate this with the occurrence of anaphylaxis iii) quantitate the isotype-specific anti-insulin and anti-peptide antibodies following B:9-23 and B:9-23RR administration iv) confirm/characterize the ability of B:9-23RR to prevent diabetes and determine if cells that block diabetes transfer have been induced v) test the generalization that B:9-23 modified to have a neutral pl prevents anaphylaxis by testing alternative C-terminus extensions of B:9-23 and finally vi) Generalize this mechanism of altered pl to a model of EAE to determine if peptide anaphylaxis seen in EAE can also be prevented with modified peptides. It is hypothesized that alteration of the pl of peptides may be a generalizable technique to prevent peptide-induced anaphylaxis while retaining immunomodulatory capacity.